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Bt toxin genes were isolated form Bacillus thuringiensis and incorporated into the several crop plants such as cotton.

The proteins encoded by the genes: CrylAc and CryllAb control the cotton bollworms and CrylAb controls corn borer.

Bt. toxin protein exists as inactive pro-toxins, but once an insect ingest this inactive toxin, it is converted into active form of toxin due to the alkaline pH of the gut which solubilize the crystal. This causes swelling and lysis of epithelial cells of midgut leading to death of insect larvae.

Gene Therapy

It is a technique of inserting genes into the cells and tissue of an individual to treat a hereditary disease.

The first clinical gene therapy was given in 1990 to a four year old girl with adenosine deaminase (ADA) deficiency. ADA enzyme is required for proper functioning at immune system.

As these cells are not immortal, the patient required periodic infusion of such genetically engineered lymphocytes.

If a functional gene is Introduced into a bone marrow cells at early embryonic stage. It could be a permanent cure of ADA deficiency.

This disorder is caused due to the deletion of the gene for adenosine deaminase enzyme. In some children ADA deficiency can be cured by bone marrow transplantation. Lymphocytes from the blood of patient are grown in a culture. A functional ADA cDNA is then introduced into these lymphocytes using retroviral vector. The lymphocytes are transferred into the body of patients.